As is well known in the art of cataract surgery, a continuous curvilinear capsulorhexis is performed on the anterior capsule to remove the natural lens. The anterior capsule has a generally smooth surface contour except at the equator, where the zonules attach. In such a case, the IOL generally remains well centered postoperatively after the continuous curvilinear capsulorhexis. However, in certain cases, the capsular bag may become decentered. For example, dehiscence or rupture of some of the zonules may cause an uneven zonular tension and decentration of the lens. If an artificial lens is situated within a capsular bag with partial zonular support, the IOL optic edge or elements of the haptic may be situated in the visual axis leading to blurred vision, monocular diplopia and optical aberrations. Contraction of the capsular bag by late fibrosis may further aggravate the vision disturbances.
Capsular tension rings have been used in patients with unstable or absent zonules during cataract surgery, with the aim of minimizing IOL decentration. The capsular tension ring may stabilize the capsular bag, may reduce asymmetric zonular forces, and may reduce capsular decentration during capsular contraction.
For example, capsular bag implants for stabilizing the capsular bag are commercially available from such manufacturers as Morcher GmbH of Stuttgart, Germany, and Hanita Lenses of Hanita, Israel. The capsular bag implant (endocapsular tension ring) comprises an open-ended loop of polymethylmethacrylate (PMMA) which is resilient to compression in the radial direction within the capsular bag. The capsular bag implant is adapted to be implanted in the residual capsular bag before or after the cataractous lens is removed, and to engage the inner peripheral surface of the residual capsular bag to prevent shrinkage. The general circular expansion of the capsular bag as provided by the capsular bag implant is purported to improve stabilization of the intraocular environment and lens centration during intraocular surgery in patients with limited zonular dialysis or generalized zonular weakness. The capsular bag implant may be sutured to the scleral wall of the eye by passing a loop around the endocapsular tension ring and then passing the suture through the annular anterior capsulorhexis flap or the peripheral edge of the capsular bag. However, passing a suture through the residual capsular bag jeopardizes the residual capsular bag's integrity and therefore jeopardizes long-term IOL centration and stabilization.
U.S. Pat. No. 5,843,184 to Cionni describes another endocapsular tension ring, purported to provide long-term stabilization and centralization of the capsular bag during and after intraocular surgery in patients having missing or damaged zonules. The endocapsular tension ring includes an open-ended loop formed of biocompatible material that is constructed to be resilient to compression in the radial direction within the capsular bag to prevent shrinkage of the capsular bag during and after intraocular surgery. The improved endocapsular tension ring includes a fixation element joined to the open-ended loop that is adapted to be attached to the scleral wall of the eye and thereby stabilize and centralize the capsular bag within the posterior chamber of the eye without passing sutures through the capsular bag.
U.S. Pat. No. 6,183,480 to Mackool describes a stabilizer or fixation device. The stabilizer includes a shaft, a stabilizing bend extending from the shaft, and a shank terminating at a termination end. The bend is between the shank and the shaft and is configured to provide a hook-like configuration to the stabilizer. A distance between a trough of the stabilizing bend and the termination end is between 1.6 mm and 5.0 mm, preferably about 2.5 mm and between 2.0 mm and 3.0 mm. The Mackool device is designed for temporary fixation and is not a device which may be permanently left in the eye.